Question

Levitt, Malta, Martin, Davis, and Cloitre (2007) evaluated the effectiveness of cognitive behavioral therapy (CBT) for treating PTSD and related symptoms for survivors of the 9/11 terrorist attacks on the World Trade Center (WTC). They used a pretest-posttest design to see if CBT was successful at reducing the symptoms of PTSD and related symptoms of depression. They used the Modified PTSD Symptom Scale Self-Report (MPSS-SR) questionnaire to measure symptoms of PTSD and the Beck Depression Inventory (BDI) self-report questionnaire to measure symptoms of depression. For both questionnaires, lower scores indicated fewer symptoms. The authors reported the following results:

Pre- to post-treatment t-tests for the WTC sample revealed significant decreases in scores on the MPSS-SR, (t(37) = 12.74, p < 0.01); as well as on the BDI (t(34) = 7.36, p < 0.01). †

(a) Was this a repeated measures design or a matched-pairs design?

(b) Which questionnaire (MPSS-SR or BDI) was completed by more participants?

MPSS-SR

OR

BDI

(c) Did the authors find support for their hypothesis? Explain.

Yes, they found support for their hypothesis. Scores on both questionnaires significantly decreased from pretest to posttest.

OR

No, they did not find support for their hypothesis. Scores on both questionnaires did not significantly change from pretest to posttest.

Answer 1

a)

repeated measures design

b)

MPSS-SR

as df for MPSS = 37 > df of BDI = 34

c)

Yes, they found support for their hypothesis. Scores on both questionnaires significantly decreased from pretest to posttest.

as p-value < 0.01